1. Field of the Invention
The present invention relates to a control system using a card-type input and output device in a control device for controlling a machine to be controlled, such as a robot control device, CNC control device, or the like.
2. Description of the Related Art
In a control device for controlling a machine which is to be controlled, such as a robot control device, CNC control device, or the like, there arise cases where data inside the control device is output externally, and cases where data and programs are input to the control device from a source that is external to the control device. Card-type devices called input/output cards are known as one means for carrying out this input and output of data and programs.
Furthermore, a PCMCIA, or the like, is known as an interface for connecting input/output cards of this kind.
FIG. 5 is a diagram for illustrating a conventional composition for connecting input/output cards to a control device. The composition of the control device 100 shown in FIG. 5 is a general composition used commonly in a variety of control devices, and only the principal constituent elements thereof are depicted. A CPU 110, ROM 114, RAM 115, and axis control circuit 116 for performing calculational and control operations are connected to a CPU bus 111. The CPU 110 performs control operations on the basis of programs stored in the ROM 114 and data stored in the RAM 115, and it controls the machine to be controlled by driving a servo amp 117 via the axis control circuit 116.
An input/output card can be connected to a control device 100 of this kind by connecting a input/output card interface 112 directly to the CPU bus 111 via a parallel bus 118, and then connecting the input/output card 4 to this input/output card interface 112.
Depending on the ease of operation and the set-up conditions of the device and machine, etc., cases may arise where operation of the input/output card 4 has to be carried out in a remove location from the control device 100.
One conceivable composition for providing a distance between the control device 100 and the input/output card 4 is to extending the length of the aforementioned parallel bus 118. However, generally, a parallel bus requires a large number of signal lines, since it uses a plurality of data lines and control lines, and hence this leads to problems in terms of increasing costs. In order to restrict cost rises in the device, it is not possible to extend the lines in the parallel bus beyond a certain length, and hence remote installation of the input/output card 4 is not practical by extension of the parallel bus.
Therefore, a composition may be conceived wherein an operating device for connecting input/output cards is provided independently from the control device, and the control device and operating device are connected together by means of a serial communications circuit. FIG. 6 is a compositional diagram for illustrating a connection between a control device and an operational device using a serial communications circuit. The compositions of the control device 100 and the operating device 200 shown in FIG. 6 are general compositions common to a variety of control devices and operating devices, and only the principal constituent elements thereof are depicted here.
In the control device 100 in FIG. 6, a CPU 110, ROM 114, RAM 115 and axis control circuit 116 are connected to a CPU bus 111, and a communications interface 114 are also connected thereto via a parallel bus 118. Moreover, in the operating device 200, a CPU 210, ROM 214, RAM 215 and an I/O interface 216 connecting key 201, etc. is connected to the CPU bus 211, and an input/output card interface 224 is also connected thereto via a parallel bus 218.
The control device 100 and operating device 200 are connected to each other by means of the communications interfaces 113,213, and a serial communications circuit 300 connecting these interfaces. An input/output card 4 connected to the input/output card interface 224 is controlled by CPU 210 in the operating device 200, and signals can be exchanged with the control device 100 via the communications interfaces 113,213, and the serial communications circuit 300.
Therefore, in a composition where the input/output card interface is connected to the parallel bus of the control device, when an input/output card is connected to the control device, operation of the input/output card is restricted to the vicinity of the host CPU of the control device, due to limitations on the length of the lines in the parallel bus, and hence it is difficult to situate an operating device for operating an I/O card in a remote location from the control device.
Moreover, in a composition where the control device and input/output card are connected by means of a serial communications circuit in order to situate this operating device at a remote location, it becomes necessary to provide a separate CPU for controlling communications on the input/output card side, thereby leading to cost increases.
It is an object of the present invention to overcome the problems associated with conventional control systems, by providing a control system which enables connecting of input/output cards using an input/output card interface, without using a CPU for controlling communications, and also by providing a control system which is capable of handling input/output cards connected at a remote location from the control device in a similar manner to input/output cards connected to the control device.
By extending the length of the parallel bus in the control device on the input/output card side, by means of serial communications, the control system according to the present invention enables an input/output card connected at a remote location from the control device to be accessed in a similar manner to a device connected to the parallel bus of the control device without using a CPU for controlling communications.
One mode of a control system according to the present invention is a control system comprising a control selection provided with a CPU (processor) for controlling a machine to be controlled, an operating section provided with an input/output card interface for enabling connection of an input/output card, and a communications circuit for conducting communications between the control section and the operating section, wherein the control section comprises a first serial communications interface for connecting to the CPU via a first communications control circuit, the operating section comprises a second serial communications interface connected to the input/output card interface via a second communications control circuit, and the communications circuit is constituted by a serial communications circuit connecting a first serial communications interface with the second serial communications interface.
Here, the machine to be controlled is a machine controlled by means of control signals, such as a robot, machine tools, or the like, whilst the control device is a robot control device, CNC control device, or the like, which implements control over the machine to be controlled.
The control section according to the present invention is a constituent element corresponding to the control device described above, and it comprises a CPU (processor) for controlling the machine to be controlled, and a ROM, RAM, axis control circuit, and the like, used together with the CPU. The CPU implements control operations on the basis of programs and the data stored in the ROM and RAM, and it controls the machine to be controlled by driving a servo motor via the axis control circuit. Moreover, the control circuit also comprises a first communications control circuit and a first serial communications interface.
The operating section according to the present invention comprises an input/output card interface which enables input/output cards to be connected, and hence it serves to provide input/output cards connection and enables access between the control section and the input/output card. For the input/output card interface, it is possible to use a card-type input/output interface such as a PCMCIA device, for example. The operating section also comprises a second communications control circuit and a second serial communications interface. It is possible to connect other devices besides input/output cards to the operating section.
In the communications circuit according to the present invention, it is also possible to constitute bi-directional communications using two-way communication by means of separate circuits for the outward and inward channels, or by means of the same circuit for the outward and inward channels. Furthermore, it is possible to apply this composition to either a full-duplex transmission system which transmits bi-directional signals by multiplexing, or a half-duplex transmission system which transmits in a single direction alternately by time division.
Moreover, with regard to the processing of data in the control section and operating section, it can also be applied either to a transmission mode for conducting serial transmission on a single line, or a transmission mode for conducting parallel transmission by a plurality of lines.
This communications circuit is controlled by the first and second communications control circuits. These communications control circuits are constituted by hardware, using an LSIs, and the like, and communications can be controlled by using the CPU on the control section side and dispensing with installation of a CPU on the operating section side.
In one embodiment of the control system according to the present invention, an input/output card is connected to an input/output card interface on the operating section side. Furthermore, a serial communications circuit is used as the communications circuit. If input/output card access is performed between the control section and the operating section, then at the operating section side, in addition to accessing the input/output card connected to the input/output card interface under the control implemented by the second communications control circuit, data and control signals are exchanged with the communications circuit via the second serial communications interface, whilst at the control section side, in addition to processing CPU access requests under the control of the first communications control circuit, data and control signals are exchanged with the communications circuit via the first serial communications interface. The first and second communications control circuits convert the parallel bus signals handled by the control section and the operating section into serial signals which they supply to the communications circuit, and furthermore, they convert serial signals received via the communications circuit into parallel bus signals.
Consequently, a composition is achieved wherein the operating section is connected to the bus on the control section side via the communications circuit, and hence the parallel bus on the control section side can be extended to the operating section side and an input/output card can be connected to the end of the parallel bus, thereby enabling the CPU in the control section to access the input/output card in a similar manner to devices connected to the parallel bus.
According, a remotely located input/output card can be accessed without using a CPU for controlling communications.
Moreover, the input/output card according to the present invention is a card-type device for conducting input and output of data and programs, for example, a card having a communications connection function, such as modem card, or a card having a memory function, such as a memory card, ATA flash disk card, or the like.
When a modem card is used as the input/output card, then data and programs can be input from and output to a further device in a remote location, by means of a telephone line, or the like, thereby enabling, for example, remote diagnosis of the control device by connecting a diagnostic device.
Moreover, in the operating section, a composition may be also be adopted wherein the second communications control circuit, in addition to being connected to the input/output card interface, is also connected to an input/output connection device for connecting input means, such as buttons, switches, etc., and output means, such as a display, printer, etc., or to an external device interface for connecting external devices, such as external memory devices, or the like, the second communications control circuit being connected to the end of the parallel bus of the control section similarly to an input/output card, thereby enabling the CPU in the control section to access same in a similar manner to devices connected to the parallel bus.
Moreover, the control section according to the present invention may be a control section comprising a robot control device or a numerical control device, and it may be applied to controlling robots or machine tools.